This invention relates to a water pump effective for use in cooling a water-cooled engine, particularly the water-cooled engine of an automotive vehicle.
A conventional water pump includes a housing, a rotary shaft freely rotatably supported in the housing via a bearing, an impeller fixedly secured to one end of the shaft, and a seal member provided between the impeller and the bearing. The seal member separates the bearing from a working chamber accommodating the impeller. A disadvantage with this seal member is that when the coolant evaporates, it is difficult for this seal member to prevent evaporated coolant from escaping. The result is leakage of coolant to the bearing side of the seal member. Such leakage of coolant into the bearing causes a decline in bearing durability. To solve this problem, Japanese Utility Model Application Laid-Open No. 3-56899 proposes a water pump in which the housing is provided with a discharge passageway that connects the space between the seal member and the bearing to the outside, thereby preventing fluid that has leaked from the seal member from reaching the bearing.
With this conventional water pump, however, the coolant that has leaked is discharged to the exterior of the housing. This results in a reduction in the amount of coolant available and, hence, a degradation in the system's cooling capability.